Drop OpenSCAD; pin cadgenbench a47c951 (STEP-only eval)

Remove the openscad apt package (the mesh-submission backend is gone) and bump
the pinned cadgenbench commit to a47c951.

Co-authored-by: Cursor <cursoragent@cursor.com>

Dockerfile

@@ -33,7 +33,6 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     && apt-get update && apt-get install -y --no-install-recommends \
         python3.12 python3.12-venv python3.12-dev \
         git ca-certificates \
-        openscad \
         libglib2.0-0 libsm6 libxext6 libgomp1 libfontconfig1 \
         libgl1 libegl1 libegl-mesa0 libxrender1 \
     && rm -rf /var/lib/apt/lists/* \
@@ -52,7 +51,7 @@ RUN python -m venv "$VIRTUAL_ENV" \
 # rebuild picks up the latest evaluator dependencies (including Open3D for
 # alignment). Lock to a commit SHA at the v1 release for reproducible scores
 # (see space-setup/post-gt-swap.md Stage F).
-ARG CADGENBENCH_SHA=e7a60e0
+ARG CADGENBENCH_SHA=a47c951
 RUN python -m pip install --no-cache-dir \
         "cadgenbench @ git+https://github.com/huggingface/cadgenbench.git@${CADGENBENCH_SHA}"